Vertical submerged pump for chemical application

ABSTRACT

The present invention discloses structural improvement of the vertical submerged pump for chemical application. The present invention is focus on reducing the crystal lump generated from high speed etching process. Structural improvement includes a shaft seal device, a diffuser and an upper inner plate. The shaft seal device offer extra flow resistance to balance the differential pressure between the inner space and pump front casing, the function are prevents air bubbles be sucked into the pump, and reduces flow leakage from the front casing into inner space, also absorbs high-pressure back-flush to avoid liquid splash in dry surface of inner space of support column. The diffuser in the support column offer extra inducer function to guides the liquid from the inner space flowing out to the tank, so as to get a stable liquid level in the inner space, thereby largely reducing splashing of the liquid. And the upper inner plate blocks the residual small amount drops from liquid splashing, to minimize producing of crystals lump from high speed etching liquid.

BACKGROUND OF THE INVENTION

a) Field of the Invention

The present invention relates to the structural improvement of avertical submerged pump for chemical application, and more particular inhigh speed etching process in PCB manufacturing, owing to the drops fromsplashing of process liquid easily become crystal when attach to drysurface and contact with air, the crystal will damage the shaft seal andlead motor to be broken, so as to reduce liquid splashing from pumpshaft to avoid generation of crystals is an important issue. The presentinvention improve the structure to control the liquid level in an innerspace of a support column of a submerged vertical pump, especial whenthe process liquid is at over upper liquid level, thereby decreasingdamage to a shaft seal of a motor, and avoiding the corrosive vaporentering into the motor to cause malfunction.

b) Description of the Prior Art

Referring to FIG. 1, a conventional vertical submerged pump is used inchemical plating or etching process to transfer strong acid, strong baseor corrosive liquid. A practical operation is described as follows. Acantilever shaft 3 be installed inside the support column 1, and at thelower side of the cantilever shaft 3 is directly connected with the hub52 of impeller 5. At rear side of the impeller 5 is provided with backvanes 51 to balance axial thrust. The impeller 5 is provided in a frontcasing 4 which is opened with an inlet port 44. A side of the frontcasing 4 is opened with an outlet port 45 which is connected to adischarge pipe 43. In a real condition, liquid sucked flow in the inletport 44 by the impeller 5 along the direction 28, is pressurized flowingthrough a flow channel of the impeller 5 and is then discharged from theoutlet port 45.

When the pump operates, the shaft sleeve 31 of the cantilever shaft 3has a tangential velocity U (as shown in FIG. 2) at outer surface, willdrive the liquid in the inner space 12 to flow in free vortex 2 with adistribution of the tangential velocity 267 shown in the drawing. Thefree vortex 2 is also provided with a stream line of a secondary flow 22with lower kinetic energy, and at the center of the vortex is formedwith a hollow space 21 which is as a funnel extended downward. A flowdirection of the free vortex 2 is also provided with the stream line ofthe secondary flow 22 on an r-z cross section at the same time, and thehollow space 21 is a primary zone where air 24 be sucked and mixed withthe liquid to produce bubbles 241, allowing the back vanes 51 to attractthe bubbles 241 to flow downward. For example, the liquid which containsbubbles 242 flows through the clearance of back cover 42 between backcover and the shaft, and then enter into the front casing 4, bubbles 242will be pressurized into bubbles 243 in smaller diameters and exportedthrough the discharge pipe 43 from the outlet port 45. The bubbles alsoflow through lower holes 11 of the support column 1, diffuser holes 112of the support column I and upper holes 111 of the support column 1 intothe tank along the direction 23.

Referring to FIG. 2, after the liquid that is close to a surface of theshaft sleeve 31 of the cantilever shaft 3 receiving kinetic energy ofrotation of the pump, a tangential velocity distribution Cu will beclose to the tangential velocity U at the outer surface of the shaftsleeve 31 of the cantilever shaft 3. However, a free surface of freevortex 2 has the energy conservation feature from Bernoulli theorem, theenergy conserve with kinetic energy, that is velocity, and potentialenergy, that is liquid level reference from tank level. The total energyis transferred from the shaft to the liquid and the free surface of thefree vortex 2 has the same energy, and the energy will convert to bothkinetic energy and potential energy, it depend on the tangentialvelocity which is low or high, if tangential velocity is low then thepotential energy must be high, that means liquid level is high. Thetangential velocity distribution Cu of the free vortex 2 decreases asthe radius r increases, and is inverse proportional to the radius r(r⁻¹); therefore, at the central part of the free vortex 2, the liquidlevel will form a funnel which is extended downward due to the fasttangential velocity, that is the maximum flow speed as same as thetangential speed of rotational shaft 3. On the other hand, as thetangential velocity Cu slow down toward the outer edge 2A of the freesurface, the potential energy will become higher, that allows the liquidlevel to be higher than both the hollow space 21 and the tank 29.

Referring to FIG. 3, when the pump discharge capacity become larger, theoutput pressure will become smaller, and at the same time if the liquidlevel of the tank 29 is lower, in this condition a low pressure suctionforce will be generated by the back vanes 51 of the impeller, owing tothe force acting on the liquid by the back vanes 51, and establish a lowpressure zone near the impeller hub 52. The pressure of the low pressurezone maybe is negative pressure in vacuum at some time, when the lowpressure is sufficient to overcome the output pressure of the pump,which liquid and air 24 will be sucked and through the clearance 42 atthe back cover into the front casing 4, especially the liquid level atthe central part of the free vortex 2 will be low. Although the supportcolumn 1 is provided with lower holes 11 to supplement the liquid fromthe tank, with the liquid flowing in along a direction 26, the liquidlevel at the outer edge surface 2A of the free vortex 2 in the innerspace 12 is as low as the liquid level in the tank 29. If this conditioncontinuously happen, the liquid level of the hollow space 21 willdescend significantly or even reach to the back cover 41, allowing theair bubbles 24 to be sucked into the front casing 4 through theclearance 42 at the back cover, which will cause the pump to operateunstably by sucking in the air bubbles and result in an unstable outputof the pump.

Referring to FIG. 4, when the pump discharge capacity is smaller, theoutput pressure become larger, and the liquid level in the tank 29 iskept high or over level limit, that is a high liquid level manufactureprocess. At this condition the low pressure suction force of the backvanes 51 is not sufficient to balance the high output pressure, and thehigh pressure liquid will leak out through the clearance 42 at the backcover 41 along a direction 262 and flow into the inner space 12. Owingto the leakage, the liquid level will increase in the inner space 12,the free surface of the free vortex 2 will rise, and especially theouter edge 2A of free vortex 2 will become higher even over the levellimit. Although the support column 1 has some openings with lower holes11, diffuser holes 112 and upper holes 111, but the circumference flow25 is in tangential flowing, owing to the liquid receiving therotational kinetic energy transferred from the shaft, so the liquid hasstrong momentum in circumferential direction and weak in radialdirection, the liquid is not easily to flow through the openings 112out, that is more liquid leakage in and less liquid flow out, the liquidwill gradually accumulate in inner space 12 of support column 1.Therefore, the liquid level at the outer edge surface 2A of the freevortex 2 will be over the level limit finally, and the liquid could bevery close to the undersurface of the motor mounted plate 61. Inaddition, some liquid will be splashed on surfaces of a seat of a V-typeoil seal 64, a ceramic seal ring 71 and a V-type oil seal 72, furtherproducing crystal lumps on these surfaces to damage the V-type oil seal72. Moreover, corrosive vapor can enter into the motor to result inmalfunction.

Referring to FIG. 5, when the pump shuts down, the impeller 5 will notgenerate high pressure any more. At this time, the high pressure liquidand compressed air in filtration tanks of the piping system will backflush 271 momentarily from the discharge pipe 43. This kind high kineticenergy is converted from pressure potential energy of compressed air andhigh pressure liquid, the back-flush 271 will flow backward out throughthe inlet port 44 along the direction 281, and will flush toward theback vanes 51 also. So back-flush 264 with high kinetic energy flowupward through the clearance 42 at the back cover 41 out, and theback-flush 265 will enter into the inner space 12, in the same time theliquid in the inner space 12 still kept in free vortex motion, such thatthe lowest level of the hollow space 21 in the vortex center cannotabsorbs the kinetic energy of back-flush 265, and part of the back-flush266 will spray and splash upward. Especially that during a high liquidlevel manufacturing process, the back-flush 266 wilt spray onto the dryundersurface 61 of the motor mounted plate, around the shaft hole 62 ofthe motor mounted plate, the ceramic seal ring 71 and the V-type oilseal 72. The spraying liquid left to produce crystals when it becomedry, this will damage the ceramic seal ring 71 and the V-type oil seal72, and further concern the liquid vapor to penetrate into the motor,which will damage motor bearing and the winding.

Concluding the aforementioned pump operation phenomena, for theapplication of a high-speed etching process, providing a low-costsolution to stop the crystal lumps formed by liquid splashing willsatisfy existing requirements of customers; whereas, issues of problemthat the solutions to be faced with are:

-   -   (1) The problem of liquid splashing at the outer edge 2A of the        free vortex 2 in the high liquid level manufacturing process,    -   (2) The problem of high pressure back flushing in the piping        system when the pump be shut down and,    -   (3) The problem that the air bubbles are sucked into the back        vanes of the impeller in the low liquid level manufacturing        process.

To completely solve the problems, each problem needs to be analyzed indetails. The cause analyses are described as follows:

-   -   (1) The liquid splashing problem: the majority issue is about        the liquid level, include the tank liquid level is at high        liquid level limit, and also the liquid leaks from front casing        into the inner space result in liquid level increasing in inner        space till over upper level limit. And another issue is the        liquid in free vortex motion in the inner space but the openings        on support column are still difficult to let the liquid flowing        out to keep the liquid level in stable.    -   (2) The back flushing problem: It is un-normal operation problem        of equipment or piping system by operator, but it always happen        because operator's problem, especially the compressed air        accumulated in filtration tanks conditions. Therefore, the pump        should be equipped with a device to isolate, guide and absorb        the pulse wave of high-pressure back-flush, that let any        operator does not worry about this.    -   (3) The air bubbles sucked-in problem: Sometimes the liquid        level in the tank could be low or beyond the low limit.        Therefore, the pump should be designed to isolate the low        pressure of the back vanes of the impeller and to guide the        liquid into the pump casing, so as to prevent larger amount air        bubbles from being sucked in to result in an unstable operation.

There are already some solutions to solve the aforementioned problems.One of the solutions is the patent TW221338, which discloses anon-contact labyrinth type seal device of a submerged vertical pump. Thepatent provides a solution to solve the problems, that the non-contactlabyrinth type seal device offer a extra flow resistance to balance thedifferential pressure between the inner space and the front casing, thatis the air bubbles will not be sucked, even a negative pressure producedfrom the back vanes of the impeller, and the high-pressure liquidflushes back from the piping will be isolated when the pump shuts down.However, this solution is not able to control the liquid at the outeredge of the vortex from splashing, and the leakage become slowly butstill leakage from front casing, it will increase the liquid levelduring the operation till to over liquid level limit, especially liquidtank has a high liquid level conditions, and the last issue of thesolution is the reliability of labyrinth type seal device.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a verticalsubmerged pump for chemical application. Structural improvement includesa shaft seal device, a diffuser and an upper inner plate. The shaft sealdevice offer extra flow resistance to balance the differential pressurebetween the inner space and pump front casing. The function are preventsair bubbles be sucked into the pump, and reduces flow leakage from thefront casing into inner space, also absorbs high-pressure back-flush toavoid liquid splash in dry surface of inner space of support column, andhas reasonable reliability. The diffuser in the support column offerextra inducer function to guides the liquid from the inner space flowingout to the tank, so as to get a stability liquid level in the innerspace, thereby largely reducing splashing of the liquid. And the upperinner plate blocks the residual small amount drops from liquidsplashing, to minimize producing of crystals lump from high speedetching liquid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As indicated in FIGS. 6, 7, 8, 9, 10 and 11, the present invention is avertical submerged pump for chemical application. The structuralimprovement includes a shaft seal device 55, a diffuser 10 in a supportcolumn and an upper inner plate 83 in a support column. The structuralimprovement comprises of:

A shaft seal device 55 having a rotor of N-type seal 53 and a stator ofN-type seal 54. The stator 54 is provided at a corresponding position inthe rotor 53 after the pump has been assembled, an out surface of therotor 53 and an inner surface of the stator 54 matching each other toform a non-contact seal channel 56. The seal channel 56 has two sharpturns with a bending angle of each turn larger than 90°, and has a morethan I mm width to improve the reliability. The stator 54 is providedwith an outer cylindrical part 543 and a plate part 548 that the stator54 can be provided on an inner wall of an upper part 46 of the frontcasing 4 by the plate part 548. The rotor 53 can be provided on animpeller hub 52 by an inner diameter 536 of the rotor. The stator 54 isprovided with two inner surfaces 549 of different radii and a conicalpart 542 which is extended downward. The rotor 53 is provided with twoinner surfaces 532 of different radii and a conical part 531. Theconical part of the stator 542 is provided to fit with the conical part531 of rotor 53, and the two form a conical part 561of the seal channel56 to extend a seal length of the seal channel 56, so the seal channel56 could offer extra flow resistance to balance the differentialpressure between the inner space 12 and the front casing 4. The firstsharp turn 564 at the seal channel 56 on the stator 54 is provided withplural radial stator holes 544 which are connected to the inner space12, and the second sharp turn 565 at the seal channel 56 on the rotor 53is provided with radial rotor holes 533 to remove impurities accumulatedto release into inner space 12, the shaft seal device could absorb thekinetic energy of the back-flush high-pressure pulse wave and guide theliquid into inner space then enter the liquid tank.

A diffuser 10 in the support column guides partially the liquiddirection from circumferential direction to radial direction, that isincrease the radial velocity component and reduce the tangentialvelocity. So the liquid will flow out in a small turning angle toincrease radial velocity, and some of the kinetic energy be convertedinto velocity in radial direction to go outward. Accordingly, thestructure of the diffuser 10 in the support column 1 could provide adiffusing function and a flow turning function to keep the liquid levelin stable at inner space 12. The diffuser blade 14 has an incident anglea between the inlet flow of the liquid and the inlet of the diffuserblade 14, such that the liquid will not change the directionsignificantly at the leading edge 141 of diffuser blade 14. After theliquid flowing through the cascade the liquid velocity will be slow downand the flow angle will be change by the diffuser blade 14, this is adiffusion process relative about some of the kinetic energy incircumference will be converted to velocity in radial flowing, and theliquid will flow out through the diffusion holes 15. So the diffuser 10can be easily manufactured and installed, as well as cost can bereduced. Three embodiments are listed as follows:

First embodiment of the diffuser 10 in the pump column 1 is pluralblades 14 with span B, which are installed inside the support column Iand arranged alternately with plural diffuser holes 112 into circular.In addition, the blades 14 are installed opposite to a direction of thecircumferential flow 25. A leading edge 141 of the diffuser blade 14faces toward the circumferential flow 25, and located above the diffuserhole 112, a trailing edge 142 of the diffuser blade is below the nextdiffuser hole 112, and a cross section 145 of the diffuser blade is asmooth arc shape. A flow channel 146 is formed between the diffuserblades 14, the diffuser hole 112 is located on the wall of the supportcolumn 1 in the flow channel 146, an inlet 147 of the flow channel isconstituted by the leading edges 141 of the neighboring diffuser blades,an outlet 148 of the flow channel is constituted by the trailing edges142 of the neighboring diffuser blades. The free vortex 2 has liquidflow 25 in horizontally circumference direction, an incident angle a isformed between the leading edge 141 of the diffuser blade and thecircumference flow 25, and the liquid enters from the inlet of the flowchannel 147 and is guided to flow downward to export from the outlet ofthe flow channel 148. When the liquid flows in the flow channel 146, thediffuser blade 14 will absorb some of the kinetic energy of the liquidto locally increase a static pressure at the flow channel 146, allowinga bigger pressure difference between the inner wall and the outer wallof the support column 1. This pressure difference allows the liquid toaccelerate out from the diffuser hole 112 and this guiding effectfacilitates expelling the excessive liquid in the inner space 12 andkeeps the liquid level stable, thereby avoiding the liquid level at theouter edge surface 2A of the vortex to reach to an upper inner plate 83of the support column.

A second embodiment of the diffuser 10 in the support column 1 is withplural diffuser holes 15 only, which are arranged in a circumference ofthe support column 1 to replace the original diffuser holes 112. Thediffuser holes 15 have an oblique opening and form a small bevel angle βwith the circumference flow 25, so as to induce the liquid to flow outby convert the tangential velocity partially to increase a radialcomponent of the velocity. When the circumference flow 25 driven by thepump shaft 3, the side wall 153 of the diffuser holes 15 will induce theflow along the wall, and another side wall 154 of the diffuser holes 15allows the liquid to turn along the diffuser holes 15, this effect issimilar like an water cut or a tongue of a volute pump casing; that is,the radial velocity component of the liquid will increase as flow 26,and more liquid will flow along the diffuser holes 15 out, and hence,the liquid will be stable by the diffuser holes 15.

A third embodiment of the diffuser 10 in the support column 1 is plurallongitudinal blades 16 with span B, which are installed in the interiorside of the support column 1, and are arranged alternately with plurallongitudinal diffuser holes 17 in circumference. The leading edge 161 ofthe diffuser blade 16 faces toward the circumference flow 25, the root162 of the diffuser blade 16 is located at the side wall 174 of the longdiffuser hole 17 and a cross section of the diffuser blade 16 is asmooth arc shape. A flow channel 166 is formed by the diffuser blades16, the inner wall of support column 1, and the longitudinal diffuserhole 17. The inlet 167 of the flow channel 166 is constituted by theleading edges 161, the outlet 168 of the flow channel 166 is thelongitudinal diffuser hole 17. The circumference flow 25 with theleading edge of the diffuser blade 161 forms an incident angle γ, theroot of the diffuser blade 162 has angle δ with the circumference. Theliquid enters from the inlet 167 of the flow channel 166, and is guidedto flow outward from the longitudinal diffuser hole 17, with smoothlyflow angle δ, so as to facilitate the liquid to flow out with the radialvelocity component of the velocity as flow 26.

An upper inner plate 83 is a ring-shape plate structure, is installed oninterior wall of the support column 1 and is closed to a lower rim ofthe upper hole 111. The cantilever shaft 3 passes through the center ofthat ring-shape structure, and keeps a large radial distance with anouter diameter of the shaft sleeve 31. When the liquid level of the freevortex 2 keeps at a certain height by the diffuser blade 14, there isstill a small amount of the liquid will splash above the support column1 from the outer edge surface of the vortex 2A. The upper inner plate 83can further isolate the splashing liquid, prohibiting the liquid toreach to a undersurface of a motor mounted plate 61, and keepingsurfaces of a seat 64 of V-type oil seal 72, a ceramic seal ring 71 anda V-type oil seal 72 clean that the V-type oil seal 72 will not bedamaged by the crystals, thereby effectively isolating acid vapor toassure that the motor will not be malfunction.

Referring to FIG. 7( a), it shows a perspective view of a shaft sealdevice 55. Referring to FIGS. 6 and 7( b), a shaft seal device 55 has arotor 53 and a stator 54, wherein after the pump has been assembled, therotor 53 is installed at a corresponding position in the inner diameter549 of the stator 54. The impeller hub 52 be fixed at the end of thecantilever shaft 3 installed with the shaft sleeve 31, and pass throughthe inner diameter 536 of the rotor. The stator 54 uses a structurehaving a plate part 548 of the stator 54 to facilitate installation andpositioning, or only a structure of an outer cylindrical part of thestator 543 is used, referring to FIG. 7( c). The stator 54 can beprovided with a screw part 547, such that the stator 54 can be installedinto a screw hole at the upper part of the front casing 46, or thestator 54 can be installed into an opening at the upper part of thefront casing 46 by other methods.

Referring to FIG. 8, it shows a cross-sectional drawing of a shaft sealdevice 55 be assembled on the vertical submerged pump. Wherein the rotor53 is a cylindrical structure which is constituted by two cylinders ofdifferent radii, the cylindrical part of the rotor 534 and the innersurface of the rotor 532 are linked together by the conical part of therotor 531 which is extended upward. At bottom of the conical part of therotor 531 is provided with plural rotor holes 533 to remove impuritieswhich be accumulated in the seal channel 56, thereby protecting the sealchannel 56 from being expanded by wearing out. The stator 54 comprisesthe plate part 548 and the outer cylindrical part 543. At interior ofthe outer cylindrical part 543 is provided with the conical part 542 ofthe stator 54 which is extended downward, and a top of the conical part542 is provided with plural radial stator holes 544 which are used totransfer the back-flush pressure wave and are connected to the innerspace 12. After the pump has been assembled, the stator 54 and the rotor53 will constitute the seal channel 56 which has an inlet 562 and anoutlet 563, the two are of different radii, as well as a conical part561 of the seal channel 56. The conical part 561 of the seal channel 56is located between the inlet 562 and the outlet 563 of the seal channel.When the liquid flows from the inlet of the seal channel 562 toward theconical part 561 of the seal channel 56, the liquid must flow backwardby more than 90° at the first sharp turn 564, and when the liquid flowsfrom the conical part of the seal channel 561 toward the outlet of theseal channel 563, the liquid should also flow backward by more than 90°at the second sharp turn 565, and vice versa when the liquid flowsreversely. A highly flow resistance loss will be produced in the sealchannel 56 with two sharp turns, even the width of seal channel 56 ismore than I mm. The conical part 561 of the seal channel 56 is formed bymatching the conical part 531 of the rotor with the conical part 542 ofthe stator, the inlet 562 and outlet 563 of the seal channel 56 areformed by the inner diameter 549 of the stator 54 and the outer diameter537 of the rotor 53, which are of different radii. The first sharp turn564 of the seal channel 56 corresponds to the plural stator holes 544which are connected to the inner space 12, and the second sharp turn 565of the seal channel 56 corresponds to the plural rotor holes 533 whichare connected with the inlet 562 and the outlet 563. A small amount ofthe high-pressure liquid in the front casing 4 will flow in from therotor holes 533, thereby removing the impurities which are accumulatedin the seat channel 56.

Referring to FIG. 9( a) when the pump operates in the low liquid levelcondition, a shaft seal device 55 offers extra flow resistance tobalance the differential pressure between the front casing 4 and innerspace 12 to avoid the air bubbles sucked into the front casing 4 frominner space 12. If the back vanes 51 generate negative pressure, thedifferential pressure will be more serious, then the seal channel 56with the second sharp turn 565 and the first sharp turn 564 can offerextra flow resistance to avoid the air 24 be sucked into the frontcasing 4. The stator holes 544 directly connect to the bottom of theinner space 12, and the less air bubbles liquid 263 could be sucked indirectly, and the stator holes 544 could offer more liquid with less airbubbles flowing in at first sharp turn 564. So the seal channel 56 couldreduce the air bubbles flowing downward

Referring to FIG. 9( b), when the liquid level 29 is normal, and thepump discharge is high capacity, the shaft seal device 55 could offerextra flow resistance to balance the differential pressure between theinner space 12 and the front casing 4, to avoid the air bubbles besucked into the front casing 4. On the contrary the pump discharge ishigh pressure, the shaft seal device 55 could offer extra flowresistance to balance the differential pressure between the inner space12 and the front casing 4, and to reduce high-pressure liquid leak fromthe front casing 4 to the inner space 12 through the seal channel 56.Partly kinetic energy of the high-pressure liquid will loss at the inletof the seal channel 562, the conical part 561, the first sharp turn 564,and the second sharp turn 565, then the outlet 563. Before changing theflow direction at the first turn 564, some of the liquid will be guidedto discharge directly from the stator holes 544 to inner space 12, therotation of the conical part 531 of the rotor 53 will increase the flowresistance. At outlet 563, as the liquid is only provided with very lowkinetic energy, the liquid level of the free vortex 2 cannot befluctuated in inner space 12. The leakage at flow direction 265 is towbut still causes the liquid level to rise, which will require thediffuser 10 in the pump column 1 to maintain the stability of the liquidlevel in the inner space 12.

Referring to FIG. 9( c), when the pump shuts down, the high-pressureliquid in the piping flushes back momentarily along the back-flushdirection 271 from the discharge pipe 43, flows back to the front casing4 and exits from the inlet port 44. Part of the high-pressure back-flushof the liquid 265 will also flush back and flow upward through the backvanes 51 and then the channel seal 56. Partly kinetic energy of thehigh-pressure back-flush of the liquid 265 will be loss at the inlet ofthe seal channel 562, the conical part 561, the first sharp turn 564,and the second sharp turn 565, then the outlet 563 of the seal channel562. At the first sharp turn 564 where the high-pressure back-flush ofthe liquid 265 will be discharged directly to the inner space 12 alongthe direction 263, and two sharp turn will changes the momentumdirection significantly. In addition, the kinetic energy of theback-flush liquid 265 will be absorbed by the conical part 561 also. Atthe end, residual of the back-flush liquid 265 will finally flow out ofthe outlet of the seal channel 563 and enter into the inner space 12. Asthe liquid is only provided with extremely low kinetic energy, theliquid splashing at the level cannot be formed at this time.

Referring to FIG. 10( a), it shows a schematic drawing of a diffuserblade 14, which is arranged with the plural diffuser holes 112 of thesupport column 1. Referring to FIG. 10( b), it shows a perspectivedrawing of a diffuser blade 16, which is arranged with the pluraldiffuser holes 17 of the support column 1.

Referring to FIG. 11, it shows a cross-sectional drawing of diffuserholes 15 only, which is arranged in circumference.

Conclude from the above, in accordance with the present invention, thepump includes the shaft seal device 55, the diffuser 10 in the pumpcolumn and the upper inner plate 83 of the support column. This low-costand simple structure can effectively isolate the air bubbles from beingsucked into the pump, maintain the stable liquid level in the innerspace and prevent the liquid from flushing back momentarily to damagethe V-type oil seal at the motor side when the pump shuts down.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional drawing of a conventional product.

FIG. 2 is a drawing of a tangential velocity of free vortex versus ashaft outer radius.

FIG. 3 is a cutaway drawing of a conventional product, a liquid level ofa tank of which is the lowest.

FIG. 4 is a cutaway drawing of a conventional product, a liquid level ofa tank of which is the highest.

FIG. 5 is a cutaway drawing of a conventional product which shuts down.

FIG. 6( a) is a cross-sectional drawing of an embedment of the presentinvention.

FIG. 6( b) is cross-sectional drawing of second embedment of the presentinvention.

FIG. 6( c) is a cross-sectional drawing of third embedment of thepresent invention.

FIG. 7( a) is a perspective drawing of a shaft seal device of thepresent invention.

FIG. 7( b) is a cross-section of a shaft seal device of the presentinvention.

FIG. 7( c) is a cross-section of a shaft seal device of the presentinvention.

FIG. 8 is a cross-sectional drawing of a shaft seal device assembled invertical submerged pump of the present invention.

FIG. 9( a) is a schematic drawing of a low liquid level operation of thepresent invention.

FIG. 9( b) is a schematic drawing of a normal liquid level operation ofthe present invention.

FIG. 9( c) is a schematic drawing of a back-flush liquid of the presentinvention.

FIG. 10( a) is a schematic drawing of a diffuser blade of the presentinvention.

FIG. 10( b) is a perspective drawing of the diffuser blade of thepresent invention.

FIG. 10( c) is another cross-sectional drawing of a diffuser blade ofthe present invention.

FIG. 11 is a cross-sectional drawing of a diffuser hole of the presentinvention.

1. A vertical submerged pump for chemical application, the structuralimprovement includes the shaft seat device, the diffuser in the pumpcolumn and the upper inner plate of the support column, their featuresare as flows: A shaft seal device has a rotor of N-type seal and astator of N-type seal, the stator is provided with an outer cylindricalpart of the stator and a plate part of the stator, the stator isinstalled in an inner surface of a pump casing by the plate part of thestator, the cylindrical stator is provided with two inner columnsurfaces of different radii and a conical part which is extendeddownward, the cylindrical rotor is provided with two outer columnsurfaces of different radii and a conical part which is extended upward,the rotor is installed on an impeller hub by an inner diameter of therotor, after the pump is assembled, the rotor is located at a relativeposition to the stator, the inner column surfaces of the stator and theouter column surfaces of the rotor match each other to form anon-contact seal channel which having two sharp turns with a bendingangle larger than 90°, and plural stator holes are located at the firstsharp turn of the seal channel on the stator to connect to an innerspace; a diffuser in a support column is provided with plural diffuserholes and plural diffuser blades, the diffuser blades are arc shape andare installed on an inner wall of the support column, the pluraldiffuser blades are arranged alternately with the plural diffuser holes,the diffuser blades are arranged opposite to the flow direction of theliquid, and the flow channel is formed by the neighboring diffuserblades, an inlet of the flow channel is constituted by leading edges ofthe neighboring diffuser blades also, and the diffuser holes are locatedon an inner wall of the support column in the flow channel, the diffuserblade has a small incident angle in horizontal circumference at theleading edge, allowing the liquid to smoothly flow into the inlet of thediffuser in the support column without changing the flow directionsignificantly; an upper inner plate of the support column which isinstalled in an interior side of the support column, and is locatedbelow an upper hole of the support column, with a center of which beingprovided with a hole to form a larger radial clearance with an outerdiameter of a shaft sleeve.
 2. The vertical submerged pump for chemicalapplication according to claim 1, wherein, a diffuser in a supportcolumn which is provided with plural diffuser holes and plural diffuserblades, the diffuser blades are arc shape and are installed on an innerwall of the support column, the plural diffuser blades are arrangedalternately with the plural diffuser holes, the leading edge of thediffuser blade of the diffuser in the support column is located abovethe diffuser holes, and the trailing edge of the diffuser blade islocated below the next diffuser hole, the diffuser blades are arrangedagainst to the flow direction of the liquid and kept an incident angleat leading edge of diffuser blade; the flow channels are formed by theneighboring diffuser blades, an inlet of the flow channel is constitutedby leading edges of the neighboring diffuser blades also, an outlet ofthe flow channel is constituted by trailing edges of the neighboringdiffuser blades and the diffuser holes are located on an inner wall ofthe support column in the flow channel.
 3. The vertical submerged pumpfor chemical application according to claim 1, wherein the diffuser inthe pump column is located in a middle or lower part of the supportcolumn.
 4. The vertical submerged pump for chemical applicationaccording to claim 1, wherein, the diffuser in the support column isformed by plural diffuser holes only, which is arranged in acircumference of the support column, the diffuser holes have an obliqueopening and form a small bevel angle against the circumference flow. 5.The vertical submerged pump for chemical application according to claim1, wherein, a diffuser in a support column which is provided with plurallongitude diffuser holes and plural longitude diffuser blades with spanB, the diffuser blades are arc shape and installed on an inner wall ofthe support column, the plural diffuser blades are arranged alternatelywith the plural diffuser holes in circumference, the root of thediffuser blade is located at the side wall of the long diffuser hole,the diffuser blades are arranged opposite to the flow direction of theliquid, and the flow channel is formed by the diffuser blades, the innerwall of support column, and the longitudinal diffuser hole, the leadingedge of the diffuser blade has an incident angle in circumference, theroot of the diffuser blade has another angle as same as the obliqueangle of diffuser hole in circumference.
 6. The vertical submerged pumpfor chemical application according to claim 1, claim 2 and claim 5,wherein, the diffuser blade is a single circular arc structure or acomplex circular arc structure.
 7. The vertical submerged pump forchemical application according to claim 1, claim 2 and claim 5, wherein,an incident angle between the leading edge of the diffuser blade and ahorizontal circumference is less than 45°.
 8. The vertical submergedpump for chemical application according to claim 1, claim 2 and claim 5,wherein, the plural diffuser blades on the support column could be madein different ways, including each blade welded on or inserted in, or anintegral cascade ring by plastic injection.
 9. The vertical submergedpump for chemical application according to claim 1, claim 2 and claim 5,wherein, the plural diffuser blade on the support column could have thesame span width or unequal span width.
 10. The vertical submerged pumpfor chemical application according to claim 1, claim 2, claim 4 andclaim 5, wherein, the plural diffuser holes on the support column couldbe longitude hole in parallel or incline hole in parallel.
 11. Thevertical submerged pump for chemical application according to claim 1,claim 2, claim 4 and claim 5, wherein, the diffuser in the supportcolumn is formed by plural diffuser holes only, the plural diffuserholes on the support column could be arranged in one row or multi-rowaround the support column.
 12. The vertical submerged pump for chemicalapplication according to claim 1 and claim 4, wherein, the diffuser inthe support column is formed by plural diffuser holes and diffuserblades, or plural diffuser holes only, which are arranged in acircumference of the support column, the diffuser holes have an obliqueopening and the oblique angle is less than 45°.
 13. The verticalsubmerged pump for chemical application according to claim 1, claim 2,claim 4 and claim 5, wherein, the diffuser in the support column isformed by plural diffuser holes and diffuser blades, the plural diffuserholes and the diffuser blades on the support column could be arranged inone row or multi-row around the support column, and the multi-row couldbe staged for each row.
 14. The vertical submerged pump for chemicalapplication according to claim 1, wherein, the diffuser in the supportcolumn is formed by plural diffuser holes and diffuser blade, which arearranged in a circumference of the support column, the diffuser holeshave an oblique opening and the oblique angle is less than 60°.
 15. Thevertical submerged pump for chemical application according to claim 1,wherein, the diffuser blades as same as the diffuser hole are longitudeholes in parallel or incline holes in parallel.
 16. A submerged verticalpump for chemical application, the structural improvement of the shaftseal device to offer extra flow resistance to separate liquid betweenthe high pressure liquid from pump casing and low pressure liquid frominner space of support column, the shaft seal device is comprised of: Ashaft seal device has a rotor of N-type seal and a stator of N-typeseal, the stator is provided with an outer cylindrical part and a platepart of the stator, the stator is installed in an inner surface of apump casing by the plate part of the stator, the cylindrical stator isprovided with two inner column surfaces of different radii and a conicalpart which is extended downward, the cylindrical rotor is provided withtwo outer column surfaces of different radii and a conical part which isextended upward, the rotor is installed on an impeller hub by an innerdiameter of the rotor, after the pump is assembled, the rotor is locatedat a relative position to the stator, the inner column surfaces of thestator and the outer column surfaces of the rotor match each other toform a non-contact seal channel which has two sharp turns with a bendingangle larger than 90°, and plural stator holes are located at the firstsharp turn of the seal channel on the stator to connect to an innerspace.
 17. The vertical submerged pump for chemical applicationaccording to claim 16, wherein, plural rotor holes are located at thesecond sharp turn of the seal channel on the rotor to connect to aninner space.
 18. The vertical submerged pump for chemical applicationaccording to claim 16, wherein, the stator is provided with an outercylindrical part of the stator and a plate part of the stator, the outercylindrical surface has a screw part, stator could be installed in innersurface of a pump casing by the screw, and till the plate part of thestator tied on the inner surface of pump front casing.
 19. A submergedvertical pump for chemical application, the structural improvement ofthe shaft seal device to offer extra flow resistance to separate liquidbetween the high pressure liquid from pump casing and low pressureliquid from inner space of support column, the shaft seal device iscomprised of: A shaft seal device has a rotor of N-type seal and astator of N-type seal, the stator is provided with an outer cylindricalpart of the stator, the stator is installed in an inner surface of apump casing, the cylindrical stator is provided with two inner columnsurfaces of different radii and a conical part which is extendeddownward, the cylindrical rotor is provided with two outer columnsurfaces of different radii and a conical part which is extended upward,the rotor is installed on an impeller hub by an inner diameter of therotor after the pump being assembled, the rotor is located at a relativeposition to the stator, the inner column surfaces of the stator and theouter column surfaces of the rotor match each other to form anon-contact seal channel which have two sharp turns with a bending anglelarger than 90°, and plural stator holes are located at the first sharpturn of the seal channel on the stator to connect to an inner space. 20.The vertical submerged pump for chemical application according to claim19, wherein, the stator is provided with an outer cylindrical part ofthe stator, the out cylindrical surface has a screw part, stator couldbe tied in an inner surface of a pump casing by the screw.